The present invention relates to novel derivatives of fortimicin B, the acid addition salts thereof and a process for preparing the same.
Fortimicins (A, B and C) are compounds belonging to pseudodisaccharide antibiotics containing 1,4-diaminocyclitol. The physical properties and antibacterial activities of these compounds, the processes of producing them by using microorganisms, and processes for separation and purification thereof from culture liquors, etc. are described in detail in U. S. Pat. Nos. 3,931,400, 3,976,768 and 4,048,015.
The planar structural formulae of the fortimicins, are illustrated in said United States Patents and their structural formulae showing absolute coordination are described in the specification of Japanese Published Unexamined Patent Application No. 5014078.
Fortimicins (A, B and C) all have antibacterial activity, but the antibacterial activity of fortimicin B is not as good as the other factors; and fortimicin A and fortimicin C are slightly unstable under strongly alkaline conditions. Therefore, compounds having more distinguished properties are in demand.
As a result of various studies, it has been found that certain 4-N-substituted derivatives of fortimicin B have enhanced antibacterial activity and good stability under alkaline conditions (Japanese Published Unexamined Patent Application No. 50140/78).
Moreover, it has now been found that certain 4,2'-di-N-substituted derivatives of fortimicin B have good stability under strongly alkaline conditions and enhanced antibacterial activity aginst a broad spectrum of pathogenic microorganism including strains resistant to known antibiotics.